The 1947 - Present Chevrolet & GMC Truck Message Board Network

Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > General Truck Forums > Electrical


Thread Tools Display Modes
Old 07-12-2018, 12:24 PM   #1
Registered User
Join Date: Sep 2015
Location: Sonoma County California
Posts: 81
What's the correct Spark Plugs?

I have a 1969 C-20 with a stock 350 and it does have HEI. I am replacing the spark plugs and plug wires with some MSD #31239 cut to fit wires.
The plugs I purchased at O'Reilly's are R43, the ones I removed are R43S.
Is that going to make a difference? The only difference I see is that the R43S is a little longer and extends farther into the combustion chamber. What would be the advantage of a longer plug?
The plugs I removed look fine, no oil build up or anything out of the ordinary so I don't think a hotter plug would be necessary...?
The AC Delco website even says the R43 plugs are the correct ones.
SonomaComa is offline   Reply With Quote
Old Yesterday, 11:49 AM   #2
Wrenchbender Ret
Registered User
Join Date: Oct 2005
Location: Lenexa, Kansas
Posts: 4,561
Re: What's the correct Spark Plugs?

The S type plugs (extended tip) came out in the 60,s & were an improvement over the regular plugs. Before long all the manufacturers switched to them. They actually run cooler then the old style plugs. The spark is closer in to the combustion chamber for faster combustion. It is best to use the S type like R43S or R44S. If an engine has the tapered seat use R44TS. The extended tip plugs cannot be used in flat head engines.
Wrenchbender Ret is offline   Reply With Quote
Old Yesterday, 03:43 PM   #3
Dead Parrot
Registered User
Join Date: Aug 2012
Location: Oklahoma City, OK
Posts: 958
Re: What's the correct Spark Plugs?

With the HEI, you can gap the plugs to .045 instead of the normal point system .035.
Dead Parrot is offline   Reply With Quote


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

All times are GMT -4. The time now is 01:50 PM.

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2018, vBulletin Solutions Inc.
Copyright 1997-2013